The present invention relates generally to treating medical conditions involving ducts and/or body lumens, for example by preventing occlusion of portions of the biliary tree.
Referring to FIG. 1, anatomical features of the biliary tree and its surroundings are shown to provide a reference for the description of the medical conditions, exemplary filter apparatuses and/or methods of ameliorating those conditions. The gall bladder 102 is the eggplant shaped sack which is connected by the cystic duct 104 to the common bile duct 106. The common bile duct 106 represents the “trunk” of the biliary tree and serves as the main conduit for transporting various bodily fluids and/or materials from the liver 116, gall bladder 102 and pancreas 110 through the Sphincter of Oddi 112 and to the small intestine (duodenum) 114.
“Stones” in the gall bladder 102 and bile ducts are found in the entire population, some of them being asymptomatic, and some—symptomatic. In the U.S., 10-15% of the adult population (more than 20 million people) suffer from bile duct stones (about 20% of the population above 65 years of age suffer from gallstones), with more than a million new cases diagnosed annually, and more than 600,000 cholecystectomy procedures performed annually. Patients with gallstones are classified according to three groups: symptomatic, asymptomatic and those suffering from complications caused by the gallstones, such as cholecystitis, pancreatitis or obstructive jaundice.
Asymptomatic patients with gallstones: Many of the patients with gallstones are completely asymptomatic and remain undiagnosed. Gallstones may be detected accidentally during evaluation of other health problems. The increasing diagnosis rate results from increased use of imaging techniques, mainly, but not exclusively, ultrasonic methods. Most of the gallstones are asymptomatic. About 10% of the patients with gallstones will develop symptoms within 5 years of diagnosis, and about 20% of them will develop symptoms within 20 years of diagnosis. The rate of symptom development is maximal during the first years following diagnosis. Entrance of the stones into the bile ducts significantly increases the incidence of complications, such as obstructive jaundice and pancreatitis, up to about 20% in 5 years.
Symptomatic gallstones: The symptoms are the most significant prognostic factors determining the need for therapeutic intervention due to the presence of gallstones. The most common symptom of gallstones is intermittent abdominal pain, located at the right upper quadrant region. The pain typically appears after meals and persists up to several hours. The pain, called “biliary colic”, is spasmodic in its nature. It varies in severity, and highly severe pain may require administration of narcotic drugs. Once the gallstones become symptomatic—there is a high probability of further symptom worsening and a high risk of disease progression to a more severe disease, such as acute cholecystitis or acute pancreatitis. About 25% of the patients will develop these complications in 10-20 years.
Complicated gallstones: Cholecystitis, stones in the common bile duct 106 (choledocholithiasis), with or without cholangitis, and pancreatitis are the most common complications of gallstone disease. Acute cholecystitis is caused by cystic duct 104 obstruction by the stones or stone particles and requires hospitalization; this condition may lead to abscess formation, gall bladder perforation, or gall bladder mucocele. Stones left in the gall bladder 102 may lead to chronic bile duct inflammation, scarring, contractures and chronic cholecystitis. A temporary bile duct obstruction causes spasmodic pain, while permanent bile duct obstruction causes inflammation and acute cholecystitis. Passage of the stones from the gall bladder 102 into the cystic duct 104 leads to obstruction of the duct, thus causing the acute clinical syndrome associated with gall bladder 102 drainage obstruction, development of spasmodic pain and acute cholecystitis. The risk for gall bladder 102 cancer is increased by gallstones, but is still very low and does not justify preventive cholecystectomy in asymptomatic patients.
Cholecystectomy eliminates most of the capacity of preserving and secreting bile after meals, and is usually considered to be a physiologically tolerable change. However, this statement is not entirely accurate. A considerable percentage of patients (sometimes up to 40%) will continue suffering from various symptoms similar to the preoperative symptoms, although less prominent and less frequent. Postoperative Duodeno gastric reflux may cause post-cholecystectomy bile gastritis. Furthermore, patients with preoperative gastro-esophageal reflux symptoms may suffer from worsening of reflux symptoms following cholecystectomy due to the increased bile content of the reflux fluids; motility changes in the upper Gastro-Intestinal (“GI”) tract may also occur after surgery. These changes, as well as impaired lipid absorption, may also contribute to post-cholecystectomy diarrhea. Fecal secondary bile acid levels are increased following cholecystectomy and in colorectal cancer patients, suggesting their involvement in colorectal cancer, as well as contribution of cholecystectomy to the development of colorectal cancer. Increased incidence of colorectal cancer following cholecystectomy has been reported, mainly in the right descending colon, more frequently in women. However, these findings require further investigation and confirmation.
The currently available treatment: gallstone dissolution and extracorporeal shock wave lithotripsy. Gallstone dissolution may be performed by chenoeoxycholic acid or ursodeoxycholic acid, or various solvents (e.g. methyl tert-butyl ether) inserted directly into the gall bladder 102 or the bile ducts using endoscopy. This treatment is often combined with extracorporeal shock wave lithotripsy or endoscopic cholecystectomy techniques. Extracorporeal shock wave lithotripsy involves extracorporeal production of computer focused shock waves by an electromagnetic or ultrasonic source in order to break up the gallstones. The stone fragments are secreted via the biliary tree into the duodenum 114.
Gallstones are suitable for dissolution therapy only if the gall bladder 102 presents at least 50% of the normal contraction capacity, the gallstones are less than 1 cm in diameter, occupy less than 40% of the gall bladder 102 volume, and are non-calcified stones of cholesterol or mixed type.
Less than 30% of all gallstones fulfill these criteria. The treatment causes maximal dissolution of gallstones during the first 6 months, but is not cost-effective after periods longer than 12 months. The treatment is associated with a failure rate of 50% and recurrence rate of 25-50%. The selection requirements for extracorporeal shock wave lithotripsy are identical to those described above for dissolution therapy. The suitable stones are small radiolucent stones smaller than 2 cm in diameter. Passage of the fragments through the cystic duct 104 and the papilla following treatment is painful, usually requiring pain management with narcotics.
Asymptomatic gallstones: Diagnosis of asymptomatic gallstones raises the question whether the patient should be referred to elective cholecystectomy due to a certain risk (2%) for the development of symptoms or complications. Most of the asymptomatic patients prefer to avoid the pain, the expenses and the risks associated with elective surgery, despite the risk of severe complications.
Symptomatic gallstones (periodic biliary colic attacks): The symptomatic patients are at increased risk for the development of complications, thus justifying the indication for cholecystectomy. The common surgical procedure is open cholecystectomy. Elective surgery, if performed during periods devoid of complications, is usually safe, with low mortality rates of only 0.1-0.5%. Since 1988, laparoscopic cholecystectomy is the preferred surgical procedure in view of the short operative time, reduced postoperative pain and discomfort and good cosmetic results. Despite these advantages, about 5% of the laparoscopic procedures are switched, in the course of surgery, to open cholecystectomy, requiring full abdominal opening. In most cases, this is due to the inability to safely identify the gall bladder 102 anatomy or to cope with intraoperative complications.
Endoscopic retrograde cholangiopancreatography (“ERCP”): An imaging technique used for the diagnosis of pancreatic, hepatic and biliary diseases, which can also be used as a therapeutic tool. The endoscope is inserted into the patient's mouth, via the esophagus, the stomach and the upper part of the small intestine. A tube is inserted through the spot into which the bile ducts are emptied, and contrast material is injected through this tube into the bile ducts, followed by a series of X-ray images enabling visualization of the bile ducts. If bile duct stenosis is observed, a stent may be inserted to alleviate stenosis. In order to perform this procedure, catheter sphincterotomy (incision through the Sphincter of Oddi 112) is performed, accompanied by balloon inflation, and finally followed by insertion of the stent into the common bile duct 106. Most of the patients with pancreatic cancer may present with obstruction of the distal part of the biliary tree and jaundice at any stage of their disease. ERCP with sphincterotomy and stent insertion is a therapeutic option providing relief for these patients. At present, EPCR is not used for insertion of stents into the gall bladder 102 itself, or into the proximal bile ducts, such as the cystic duct 104, and the method does not enable treatment of gallstones—especially gallstones located in the gall bladder 102 itself.
Nephrolithiasis is a common disease that is estimated to incur medical costs of $2.1 billion per year in the United States alone. Nephrolithiasis specifically refers to calculi in the kidneys (renal calculi), but renal calculi and ureteral calculi (ureterolithiasis) are often related. Ureteral calculi almost always originate in the kidneys, although they may continue to grow once they lodge in the ureter.
Urinary tract stone disease is likely caused by two basic phenomena. The first phenomenon is supersaturation of the urine by stone-forming constituents, including calcium, oxalate, and uric acid. Crystals or foreign bodies can act as nidi, upon which ions from the supersaturated urine form microscopic crystalline structures. The overwhelming majority of renal calculi contain calcium. Uric acid calculi and crystals of uric acid, with or without other contaminating ions, comprise the bulk of the remaining minority. The second etiology, which is most likely responsible for calcium oxalate stones, is deposition of stone material on a renal papillary calcium phosphate nidus, typically a Randall plaque.
The lifetime prevalence of urinary tract stone disease in the United States is approximately 10%. The annual incidence of urinary tract stones in the industrialized world is estimated to be 0.2%. The likelihood that a white male will develop stone disease by age 70 years is 1 in 8. Stones of the upper urinary tract are more common in the United States than in the rest of the world. Roughly two million patients present on an outpatient basis with stone disease each year in the United States, which is a 40% increase from 1994.